Synergistically optimizing thermoelectric performance of ZnO ceramics by interfacial band alignment and self-doping defects

ZnO is a promising thermoelectric ceramic material due to non-toxicity and abundance in resources. However, its thermoelectric performance is limited by the intrinsic low carrier concentration and high thermal conductivity. In this work, we synthesized the (1 - x)ZnO/xZnS (x = 0-0.05) powders by a two-step solution method followed by microwave sintering in an oxygen-deficient environment at 1000 celcius, and then produced the self-doped ZnO ceramics with ZnO/ZnS interfaces. The electrical and thermal properties was investigated from room temperature to 900 K. The ZnO/ZnS interface and self-doping significantly increased the electrical properties of ZnO ceramics, the electrical conductivity (sigma) and Seebeck coefficient (alpha) increased simultaneously with temperature for (1 - x)ZnO/xZnS (x > 0), and the highest power factor (PF, 3675 mu WGreek ano teleiam- 1Greek ano teleiaK- 2) was obtained from 0.98ZnO/ 0.02ZnS at 900 K. At the same time, the ZnO/ZnS interfaces and self-doped defects greatly reduced the lattice thermal conductivity. Finally, the highest ZT value of 0.94 has been reached in 0.95ZnO/0.05ZnS at 900 K.